Modulation of functional network properties in major depressive disorder following electroconvulsive therapy (ECT): a resting-state EEG analysis

Abstract

Electroconvulsive therapy (ECT) is a highly effective neuromodulatory intervention for treatment-resistant major depressive disorder (MDD). Presently, however, understanding of its neurophysiological effects remains incomplete. In the present study, we utilised resting-state electroencephalography (RS-EEG) to explore changes in functional connectivity, network topology, and spectral power elicited by an acute open-label course of ECT in a cohort of 23 patients with treatment-resistant MDD. RS-EEG was recorded prior to commencement of ECT and again within 48 h following each patient’s final treatment session. Our results show that ECT was able to enhance connectivity within lower (delta and theta) frequency bands across subnetworks largely confined to fronto-central channels, while, conversely, more widespread subnetworks of reduced connectivity emerged within faster (alpha and beta) bands following treatment. Graph-based topological analyses revealed changes in measures of functional segregation (clustering coefficient), integration (characteristic path length), and small-world architecture following ECT. Finally, post-treatment enhancement of delta and theta spectral power was observed, which showed a positive association with the number of ECT sessions received. Overall, our findings indicate that RS-EEG can provide a sensitive measure of dynamic neural activity following ECT and highlight network-based analyses as a promising avenue for furthering mechanistic understanding of the effects of convulsive therapies.

Changes in brain network properties in major depressive disorder following electroconvulsive therapy: a combined static and dynamic functional magnetic resonance imaging study

“…The increases in E loc and E p reflect that the brain network is more regularized with enhanced information transfer efficiency between nodes and less energy costs (56). Thus, it could be hypothesized that ECT may have effects to decrease the randomness of brain network as reflected by elevated levels of E loc and E p , which has been reported in a series of previous studies (52)(53)(54) and confirmed in the present study again. that an important dynamic brain network metric named flexibility was significantly decreased, which suggests a significantly decreased temporal variability (increased temporal stability) of brain network after the ECT in MDD patients (Figure 1).…”

Clinical EEG slowing induced by electroconvulsive therapy is better described by increased frontal aperiodic activity

“…Despite this, the neural mechanism behind EEG slowing remains unclear. In addition, how this increase in spectral power in the low frequency range is related to clinical outcome remains ambiguous 10 : several studies link EEG "slowing" to clinical ECT improvement 4,5,[11][12][13] , some show the inverse relationship 14,15 , and others find no significant relationship 7,[16][17][18] .…”

Multimodal multi-center analysis of electroconvulsive therapy effects: brainwide gray matter increase without functional changes

“…Although the resting-state data used in this study was not optimal and limited by the relatively minimal acquisition time (6 to 8 minutes), and the fact that the effects of ECT on resting-state activity could occur during the entire ECT-course instead of within two weeks after the last session, it may be possible that BOLD-signal fluctuations are just not always sensitive to ECT effects on brain function. Rather, ECT effects could more accurately be studied in brain activity measures such as specific EEG frequency bands [48-49], which is also more analogous to the ictal mechanism behind ECT. The biological processes occurring during and after ECT may also involve other processes such as molecular neurotransmission effects, since alterations in serotonergic 5-HT1A and 5-HT2A receptor binding and transmission following ECT have been reported, both in the hippocampus and frontal affective areas (50-51).…”

“…Although the resting-state data used in this study was not optimal and limited by the relatively minimal acquisition time (6 to 8 minutes), and the fact that the effects of ECT on resting-state activity could occur during the entire ECT-course instead of within two weeks after the last session, it may be possible that BOLD-signal fluctuations are just not always sensitive to ECT effects on brain function. Rather, ECT effects could more accurately be studied in brain activity measures such as specific EEG frequency bands [48][49],…”